1. Field of the Invention
The present invention relates generally to adapters for coupling optical fiber and in particular to adapters that facilitate panel mounting.
2. Prior Art
Fiber optic transmission is commonly effected through an optical fiber assembly consisting of a length of optical fiber and an interconnection including two connectors terminated on the optical fiber and then mated together via a female-to-female adapter. This interconnection facilitates testing along cable segments, enables re-routing, and facilitates changes in floor plans within a building. Especially in a Fiber-to-the-Desk application, the transmission is usually via a duplexed interconnection; i.e., the cable encompasses two fibers and the corresponding individual (simplex) connectors and adapters are linked together to form a double (duplex) interconnection.
There are two connector interfaces commonly utilized for data and telephone communication systems and their designations are ST and SC. The ST is a push-on/twist-lock interface. Most duplex ST adapters consist of two (2) identical, basically rectangular bodies which are welded together. The adapters are mounted through an oval or rectangular panel cut-out and are then retained to the panel via use of screws which fit through clearance holes in the adapter body's mounting flange and then threaded into tapped holes in the panel (on both sides of cut-out). The ST simplex adapter is cylindrical and the desired anti-rotation is typically effected via use of a flat (or flats) in the cylindrical mounting surface and a corresponding "D" (or "double-D") panel cut-out.
The SC is a push-on only connector. There is no locking mechanism other than retention latches that engage a connector which effect a retention that resists casual disengagement. Due to the inherent intramating differences, the means of attaching the adapters to a panel differ as well. The SC adapter is rectangularly shaped and, hence, the cut-out in the panel into which the SC adapter is to be mated is also rectangular. The SC adapter is rectangular-shaped and is typically retained within a rectangular panel cut-out (the size of which is larger than the oval/rectangular ST panel cut-out) via the use of separate, stamped and formed metallic (usually stainless steel) mounting "clips" which are attached to the adapter. The clip design is such that there is a retaining member on each side of the adapter and a flexible segment of each clip's retaining member collapses inwardly as the adapter passes through the panel cut-out and then snaps back to its original, outward position after it clears the panel thickness. In this position, the clips serve to retain the adapter within the panel. The other SC adapter mounting option is to use screws which fit through clearance holes in the adapter mounting flange and then thread into corresponding tapped holes in the panel (on both sides of the rectangular cut-out) in a similar manner to one of the ST mounting options.
Due to the differing mounting styles, the manufacturer of such products must design the products to include a panel cut-out for the ST and another panel cut-out for the SC. Producing two different types of panel cut-outs increases manufacturing costs and inventory requirements and complexity. Accordingly, there is a perceived need in the art for adapters that can fit into a single panel cut-out style.
Another problem encountered in the prior art is that the use of metallic mounting clips to mount the SC style adapter to the panel. These metallic mounting clips increase the cost of each unit and require additional assembly and inventory by the manufacturer.
FIG. 1A is a cross-sectional view of a conventional adapter body shown generally at 1. An "adapter" includes two "adapter bodies" that are joined together. The adapter body 1 includes an adapter housing 2 which is a generally rectangular housing having two separate adapter cavities 3. Ultrasonic energy directors 4a provide for mounting an adapter body 1 to another adapter body. The adapter body 1 includes a separating member 6 that isolates each of the adapter cavities 3. FIGS. 1B and 1C are front and rear views of the adapter body 1 shown in FIG. 1A. FIG. 2A is a cross-sectional view of a retention latch shown generally at 10. A retention latch 10 is placed within each of the adapter cavities 3 to hold a connector formed on the end of the optical fiber. The retention latch includes a pair of resilient fingers 12 that hold the connector in the retention latch 10. The fingers 12 include a tapered opening 14 that ease insertion of the connector into the retention latch 10. Each finger 12 includes a shoulder 16 that creates an interference fit with a portion of the connector. The fingers 12 grip a segment of the installed connector and retain the connector within the retention latch 10 so as to effect a withdrawal force of typically 3 pounds. A central conduit 18 includes a ferrule opening 20 that receives the tip of the connector. A retention latch opening 22 receives an alignment sleeve that aligns the ends of the optical fibers fitted to the adapter.
The prior art adapter uses simplex retention latches 10. Thus, an adapter assembly includes two adapter bodies 1, which are mounted face to face, and four simplex retention latches 10. Requiring four simplex retention latches 10 has several drawbacks. First, the manufacturer must stock additional parts which can become lost or damaged. Second, it takes a long amount of time to assemble the four simplex retention latches.
Another problem with the retention latches of the prior art is that the retention latches are not held in the adapter bodies firmly. When an assembler must transport the adapter body, including the retention latches, to a welding area for final joining of two adapter bodies, the retention latches may become misaligned or fall out of the adapter body.